Understanding how the wealth of genetic data in current genome sequences translates into functionally significant traits is a fundamental goal in genome research. An emerging powerful approach to this question compares closely related species with elemental differences in key morphological traits in order to identify genes that give rise to important organismal features. Comparing genetic sequences and expression profiles across these species allows an understanding of morphological novelty, regulation of morphogenesis, and molecular evolution at morphologically critical genes. The goals of the proposed research are two-fold: to identify genes responsible for sperm morphology, and to survey those genes in closely related species with variable sperm morphology in order to understand the relationship between genetic variation and morphologically important modifications. This project will be implemented using sea urchins, aided by a vast understanding of their reproductive and developmental biology as well as an ongoing genome sequencing project. The results of this research promise future applications to fertility studies in humans as well as a greater understanding of how genotype influences phenotype. [unreadable] [unreadable]